Synthesis method of perfluoroisobutyronitrile

Abstract

The present invention belongs to the field of fluoride preparation, and specifically relates to a method for synthesizing perfluoroisobutyronitrile, comprising the following steps: S1: using hexafluoroacetone as a raw material and p-methylbenzenesulfonylmethyl isocyanide as a cyanating agent, under the action of alkali, alcohol and aprotic solvent, 3,3,3-trifluoro-2-(trifluoromethyl)propionitrile is prepared; S2: 3,3,3-trifluoro-2-(trifluoromethyl)propionitrile is fluorinated to obtain perfluoroisobutyronitrile. The technical solution of the present application uses hexafluoroacetone as a raw material and p-methylbenzenesulfonylmethyl isocyanide as a cyanide source, and performs a cyanation reaction under the action of a catalyst and a solvent. This reaction has the advantages of mild conditions, high safety and high conversion rate. And the solvent of the process can be recycled, and the subsequent purification and treatment of perfluoroisobutyronitrile is simple, which is suitable for large-scale production.

Description

Technical Field

[0001] The invention belongs to the field of fluoride preparation, and specifically relates to a method for synthesizing perfluoroisobutyronitrile. Background Art

[0002] Perfluoroisobutyronitrile is an important fluorine-containing fine chemical in perfluoronitrile compounds. Due to its excellent insulation performance, arc extinguishing performance, good material compatibility, low toxicity, no flash point, and low GWP value, perfluoroisobutyronitrile can be used as an insulating gas to replace traditional SF6 and has good application prospects.

[0003] Considering the product yield, raw material cost and production safety, the current method for preparing perfluoroisobutyronitrile that is easy to scale up industrially mainly includes the following steps:

[0004] 1. Prepare intermediates such as perfluoroisobutyryl fluoride and perfluoroisobutyric acid by electrolysis or chemical synthesis;

[0005] 2. Esterifying the intermediate to prepare perfluoroisobutyrate;

[0006] 3. preparing perfluoroisobutyramide by ammoniation of perfluoroisobutyrate;

[0007] 4. Dehydrate perfluoroisobutyramide in the presence of a dehydrating agent to prepare perfluoroisobutyronitrile and purify it.

[0008] The raw materials of this method, perfluoroisobutyryl fluoride or methyl perfluoroisobutyrate, are difficult to obtain, and large-scale production is difficult. Ammonia is used in the production process, and the production process has certain risks. In addition, the yield of the amination step and the dehydration step in this method is low, resulting in a low overall yield of perfluoroisobutyronitrile. Summary of the invention

[0009] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a method for synthesizing perfluoroisobutyronitrile.

[0010] To achieve the above object, the technical solution adopted by the present invention is:

[0011] A method for synthesizing perfluoroisobutyronitrile comprises the following steps: S1: using hexafluoroacetone as a raw material and p-methylbenzenesulfonylmethyl isocyanide as a cyanation reagent, under the action of a base, an alcohol and an aprotic solvent, 3,3,3-trifluoro-2-(trifluoromethyl)propionitrile is prepared; S2: fluorinating 3,3,3-trifluoro-2-(trifluoromethyl)propionitrile to obtain perfluoroisobutyronitrile.

[0012] The specific steps of step S2) are: S2.1) brominating 3,3,3-trifluoro-2-(trifluoromethyl)propionitrile to obtain 2-bromo-3,3,3-trifluoro-2-(trifluoromethyl)propionitrile; S2.2) fluorinating 2-bromo-3,3,3-trifluoro-2-(trifluoromethyl)propionitrile to obtain perfluoroisobutyronitrile.

[0013] Prepared by the following formula (I):

[0014] (I).

[0015] The specific steps of step S1) are: adding p-toluenesulfonylmethyl isocyanide, alcohol, aprotic solvent and base into a reaction kettle respectively, stabilizing the temperature of the reaction kettle at -10°C and then evacuating to vacuum, then introducing hexafluoroacetone and stabilizing the reaction kettle at the reaction temperature to react; after the reaction is completed, discharging the material in the kettle and filtering and separating the liquids, collecting the lower fluorinated layer, and obtaining 3,3,3-trifluoro-2-(trifluoromethyl)propionitrile;

[0016] Preferably, the molar ratio of hexafluoroacetone to p-toluenesulfonylmethyl isocyanide is 1:1-3; more preferably, the molar ratio of hexafluoroacetone to p-toluenesulfonylmethyl isocyanide is 1:1.8-2;

[0017] Preferably, the mass ratio of hexafluoroacetone to the aprotic solvent is 1:3-5; more preferably, the mass ratio of hexafluoroacetone to the aprotic solvent is 1:3.5-4;

[0018] Preferably, the molar ratio of hexafluoroacetone to the base is 1:2-10; more preferably, the molar ratio of hexafluoroacetone to the base is 1:3-5.5;

[0019] Preferably, the mass ratio of hexafluoroacetone to alcohol is 1:0.5-2; more preferably, the mass ratio of hexafluoroacetone to alcohol is 1:0.8-1.5;

[0020] Preferably, the reaction temperature is -10 to 20°C; more preferably, the reaction temperature is -5 to 0°C.

[0021] Preferably, the base is one or more of lithium hydroxide, sodium hydroxide, potassium hydroxide, cesium hydroxide, sodium carbonate, potassium carbonate, sodium phosphate, potassium phosphate, sodium methoxide, potassium methoxide, sodium ethoxide, potassium ethoxide, sodium n-propoxide, sodium isopropoxide, potassium isopropoxide, sodium n-butoxide, sodium tert-butoxide, potassium tert-butoxide, sodium hydride, potassium hydride, and calcium hydride;

[0022] The alcohol is one or more of methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, 2-methyl-1-propanol, and 2-methyl-2-propanol;

[0023] The solvent is one or more of dimethyl ether, ethyl ether, propyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, acetonitrile, chloroform, N,N-dimethylformamide, sulfolane, toluene, 1,4-dioxane and N-methylpyrrolidone.

[0024] The specific steps of step S2.1) are: adding 3,3,3-trifluoro-2-(trifluoromethyl)propionitrile, aprotic solvent, and liquid bromine into a reaction kettle, and gradually raising the temperature of the reaction kettle to the required reaction temperature. After the reaction is completed, sodium bisulfite solution is added to the reaction kettle and separated to obtain 2-bromo-3,3,3-trifluoro-2-(trifluoromethyl)propionitrile;

[0025] Preferably, the method for judging the end of the reaction is: during the reaction process, the system liquid is collected for gas chromatography testing to analyze the system composition; when the 3,3,3-trifluoro-2-(trifluoromethyl)propionitrile in the reaction kettle is completely consumed, it indicates that the reaction is over;

[0026] Preferably, the molar ratio of 3,3,3-trifluoro-2-(trifluoromethyl)propionitrile to liquid bromine is 1:1.2-4; more preferably, the molar ratio of 3,3,3-trifluoro-2-(trifluoromethyl)propionitrile to liquid bromine is 1:1.5-2.5;

[0027] Preferably, the mass ratio of 3,3,3-trifluoro-2-(trifluoromethyl)propionitrile to the aprotic solvent is 1:1-3; more preferably, the mass ratio of 3,3,3-trifluoro-2-(trifluoromethyl)propionitrile to the aprotic solvent is 1:1.5-2;

[0028] Preferably, the reaction temperature is 10-50°C; more preferably 25-35°C.

[0029] The results show that the yield of this step is higher within the preferred range.

[0030] The specific steps of step S2.2) are:

[0031] Add 2-bromo-3,3,3-trifluoro-2-(trifluoromethyl)propionitrile, hydrogen fluoride and metal fluoride into a reaction kettle, and gradually increase the temperature of the reaction kettle to the required temperature for reaction. After the reaction is completed, cool the reaction kettle to 10°C, release the gas in the kettle and wash it with alkali solution to obtain perfluoroisobutyronitrile;

[0032] Preferably, the method for judging the end of the reaction is: observing the pressure change in the reactor during the reaction, collecting gas samples in the reactor for infrared testing, and analyzing the gas composition; when the pressure in the reactor is stable and there is no 2-bromo-3,3,3-trifluoro-2-(trifluoromethyl)propionitrile and only the characteristic peak of perfluoroisobutyronitrile in the infrared spectrum, it indicates that the reaction is over;

[0033] Preferably, the molar ratio of 2-bromo-3,3,3-trifluoro-2-(trifluoromethyl)propionitrile to hydrogen fluoride is 1:4-12; more preferably, the molar ratio of 2-bromo-3,3,3-trifluoro-2-(trifluoromethyl)propionitrile to hydrogen fluoride is 1:6-9;

[0034] Preferably, the metal fluoride is one or more of CsF, AlF3, SbF5;

[0035] Preferably, the molar ratio of 2-bromo-3,3,3-trifluoro-2-(trifluoromethyl)propionitrile to the metal fluoride is 1:1-5; more preferably, the molar ratio of 2-bromo-3,3,3-trifluoro-2-(trifluoromethyl)propionitrile to the metal fluoride is 1:1.5-3;

[0036] Preferably, the reaction temperature is 60-100°C; more preferably 70-80°C.

[0037] Likewise, the results show that the yield of this step is higher within the preferred range.

[0038] Compared with the prior art, the present invention has the following beneficial effects:

[0039] The technical solution of the present application uses hexafluoroacetone as a raw material and p-toluenesulfonylmethyl isocyanide as a cyanide source, and performs a cyanation reaction under the action of a catalyst and a solvent. This reaction has the advantages of mild conditions, low toxicity, high safety, and high conversion rate. The obtained product can be brominated and fluorinated to obtain perfluoroisobutyronitrile. The method has simple equipment, low investment and operation and maintenance costs, is easy and safe to operate, and has a high overall yield of perfluoroisobutyronitrile. In addition, the solvent in this process can be recycled, and the subsequent purification and treatment of perfluoroisobutyronitrile is simple, which is suitable for large-scale production. DETAILED DESCRIPTION

[0040] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention is further described in detail below in conjunction with the best embodiment. Example 1

[0041] A method for synthesizing perfluoroisobutyronitrile comprises the following steps:

[0042] S1. Add 25.4g (0.13mol) of p-methylbenzenesulfonylmethyl isocyanide, 9g of methanol, 67g of diethylene glycol dimethyl ether and 36.6g (0.3mol) of potassium tert-butoxide to a 500mL stirred reactor, stabilize the reactor temperature at -10°C and evacuate to vacuum, then introduce 16.6g (0.1mol) of hexafluoroacetone and stabilize the reactor temperature at -10°C for reaction. After the reaction is completed, discharge the materials in the reactor and filter and separate the liquids, collect the lower fluorinated layer, and obtain 3,3,3-trifluoro-2-(trifluoromethyl)propionitrile.

[0043] S2.1. Add 17.7g (0.1mol) 3,3,3-trifluoro-2-(trifluoromethyl)propionitrile, 24g (0.15mol) liquid bromine, and 35.4g chloroform to a 250mL stirred reactor, and set the reactor temperature to 25°C. During the reaction, collect the system liquid for gas chromatography testing. When the 3,3,3-trifluoro-2-(trifluoromethyl)propionitrile in the reactor is completely consumed, stop the reaction and cool the reactor to 0°C. Add sodium bisulfite solution to the reactor, and when the system becomes colorless, separate 2-bromo-3,3,3-trifluoro-2-(trifluoromethyl)propionitrile.

[0044] S2.2. Add 25.6g (0.1mol) 2-bromo-3,3,3-trifluoro-2-(trifluoromethyl)propionitrile, 8g (0.4mol) HF, and 33g (0.15mol) SbF5 to a 250mL stirred reactor, and gradually increase the reactor temperature to 60°C. During the reaction, collect system gas for infrared testing. When the 2-bromo-3,3,3-trifluoro-2-(trifluoromethyl)propionitrile in the reactor is completely consumed, stop the reaction and cool the reactor to 10°C. Release the reactor gas, and wash with alkali solution to obtain perfluoroisobutyronitrile, with a total yield of 82% and a purity of 99%. Example 2

[0045] A method for synthesizing perfluoroisobutyronitrile comprises the following steps:

[0046] S1. Add 39g (0.2mol) of p-methylbenzenesulfonylmethyl isocyanide, 16.6g of 2-methyl-1-propanol, 85g of triethylene glycol dimethyl ether and 19.2g (0.2mol) of sodium n-butoxide to a 500mL stirred reactor, stabilize the reactor temperature at -10°C and evacuate to vacuum, then introduce 16.6g (0.1mol) of hexafluoroacetone and stabilize the reactor temperature at -5°C for reaction. After the reaction is completed, discharge the materials in the reactor and filter and separate the liquids, collect the lower fluorinated layer, and obtain 3,3,3-trifluoro-2-(trifluoromethyl)propionitrile.

[0047] S2.1. Add 17.7g (0.1mol) 3,3,3-trifluoro-2-(trifluoromethyl)propionitrile, 19.2g (0.12mol) liquid bromine, and 18g DMF to a 250mL stirred reactor, and set the reactor temperature to 35°C. During the reaction, collect the system liquid for gas chromatography testing. When the 3,3,3-trifluoro-2-(trifluoromethyl)propionitrile in the reactor is completely consumed, stop the reaction and cool the reactor to 0°C. Add sodium bisulfite solution to the reactor, and when the system becomes colorless, separate 2-bromo-3,3,3-trifluoro-2-(trifluoromethyl)propionitrile.

[0048] S2.2. Add 25.6g (0.1mol) 2-bromo-3,3,3-trifluoro-2-(trifluoromethyl)propionitrile, 12g (0.6mol) HF, and 42g (0.5mol) AlF3 to a 250mL stirred reactor, and gradually increase the reactor temperature to 70°C. During the reaction, collect system gases for infrared testing. When the 2-bromo-3,3,3-trifluoro-2-(trifluoromethyl)propionitrile in the reactor is completely consumed, stop the reaction and cool the reactor to 10°C. Release the reactor gas, and wash with alkali solution to obtain perfluoroisobutyronitrile, with a total yield of 84% and a purity of 99%. Example 3

[0049] A method for synthesizing perfluoroisobutyronitrile comprises the following steps:

[0050] S1. Add 35g (0.18mol) of p-methylbenzenesulfonylmethyl isocyanide, 13.5g of ethanol, 50g of acetonitrile and 27g (0.5mol) of sodium methoxide to a 500mL stirred reactor, stabilize the reactor temperature at -10℃ and evacuate to vacuum, then introduce 16.6g (0.1mol) of hexafluoroacetone and stabilize the reactor temperature at 0℃ for reaction. After the reaction is completed, discharge the materials in the reactor and filter and separate the liquids, collect the lower fluorinated layer, and obtain 3,3,3-trifluoro-2-(trifluoromethyl)propionitrile.

[0051] S2.1. Add 17.7g (0.1mol) 3,3,3-trifluoro-2-(trifluoromethyl)propionitrile, 35g (0.2mol) liquid bromine, and 54g acetonitrile to a 250mL stirred reactor, and set the reactor temperature to 30°C. During the reaction, collect the system liquid for gas chromatography testing. When the 3,3,3-trifluoro-2-(trifluoromethyl)propionitrile in the reactor is completely consumed, stop the reaction and cool the reactor to 0°C. Add sodium bisulfite solution to the reactor, and when the system becomes colorless, separate 2-bromo-3,3,3-trifluoro-2-(trifluoromethyl)propionitrile.

[0052] S2.2. Add 25.6g (0.1mol) 2-bromo-3,3,3-trifluoro-2-(trifluoromethyl)propionitrile, 16g (0.8mol) HF, and 25.2g (0.3mol) AlF3 to a 250mL stirred reactor, and gradually increase the reactor temperature to 80°C. During the reaction, collect system gases for infrared testing. When the 2-bromo-3,3,3-trifluoro-2-(trifluoromethyl)propionitrile in the reactor is completely consumed, stop the reaction and cool the reactor to 10°C. Release the reactor gas, and wash with alkali solution to obtain perfluoroisobutyronitrile, with a total yield of 87% and a purity of 99%. Example 4

[0053] A method for synthesizing perfluoroisobutyronitrile comprises the following steps:

[0054] S1. Add 19.5g (0.1mol) of p-methylbenzenesulfonylmethyl isocyanide, 25g of 2-propanol, 60g of tetraethylene glycol dimethyl ether and 40g (1mol) of sodium hydroxide to a 500mL stirred reactor, stabilize the reactor temperature at -10°C and evacuate to vacuum, then introduce 16.6g (0.1mol) of hexafluoroacetone and stabilize the reactor temperature at 10°C for reaction. After the reaction is completed, discharge the materials in the reactor and filter and separate the liquids, collect the lower fluorinated layer, and obtain 3,3,3-trifluoro-2-(trifluoromethyl)propionitrile.

[0055] S2.1 Add 17.7g (0.1mol) 3,3,3-trifluoro-2-(trifluoromethyl)propionitrile, 64g (0.4mol) liquid bromine, and 27g triethylene glycol dimethyl ether to a 250mL stirred reactor, and set the reactor temperature to 50°C. During the reaction, collect the system gas for infrared testing. When the 3,3,3-trifluoro-2-(trifluoromethyl)propionitrile in the reactor is completely consumed, stop the reaction and cool the reactor to 0°C. Add sodium bisulfite solution to the reactor, and when the system becomes colorless, separate 2-bromo-3,3,3-trifluoro-2-(trifluoromethyl)propionitrile.

[0056] S2.2. Add 25.6g (0.1mol) 2-bromo-3,3,3-trifluoro-2-(trifluoromethyl)propionitrile, 18g (0.9mol) HF, and 30g (0.2mol) CsF to a 250mL stirred reactor, and gradually increase the reactor temperature to 100°C. During the reaction, collect system gas for gas chromatography testing. When the 2-bromo-3,3,3-trifluoro-2-(trifluoromethyl)propionitrile in the reactor is completely consumed, stop the reaction and cool the reactor to 10°C. Release the reactor gas, and wash with alkali solution to obtain perfluoroisobutyronitrile, with a total yield of 80% and a purity of 99%. Example 5

[0057] A method for synthesizing perfluoroisobutyronitrile comprises the following steps:

[0058] S1. Add 58.5g (0.3mol) of p-toluenesulfonylmethyl isocyanide, 32g of n-butanol, 83g of acetonitrile and 50g (0.6mol) of potassium ethoxide to a 500mL stirred reactor, stabilize the reactor temperature at -10°C and evacuate to vacuum, then introduce 16.6g (0.1mol) of hexafluoroacetone and stabilize the reactor temperature at 20°C for reaction. After the reaction is completed, discharge the materials in the reactor and filter and separate the liquids, collect the lower fluorinated layer, and obtain 3,3,3-trifluoro-2-(trifluoromethyl)propionitrile.

[0059] S2.1 Add 17.7g (0.1mol) 3,3,3-trifluoro-2-(trifluoromethyl)propionitrile, 40g (0.25mol) liquid bromine, and 36g chloroform to a 250mL stirred reactor, and set the reactor temperature to 10°C. During the reaction, collect the system liquid for gas chromatography testing. When the 3,3,3-trifluoro-2-(trifluoromethyl)propionitrile in the reactor is completely consumed, stop the reaction and cool the reactor to 0°C. Add sodium bisulfite solution to the reactor, and when the system becomes colorless, separate 2-bromo-3,3,3-trifluoro-2-(trifluoromethyl)propionitrile.

[0060] S2.2 Add 25.6g (0.1mol) 2-bromo-3,3,3-trifluoro-2-(trifluoromethyl)propionitrile, 24g (1.2mol) HF, and 21.7g (0.1mol) SbF5 to a 250mL stirred reactor, and gradually increase the reactor temperature to 60°C. During the reaction, collect system gases for infrared testing. When the 2-bromo-3,3,3-trifluoro-2-(trifluoromethyl)propionitrile in the reactor is completely consumed, stop the reaction and cool the reactor to 10°C. Release the reactor gas, and wash with alkali solution to obtain perfluoroisobutyronitrile, with a total yield of 81% and a purity of 99%.

[0061] From the above, it can be seen that the technical solution of the present application uses hexafluoroacetone as a raw material and p-toluenesulfonylmethyl isocyanide as a cyanide source, and performs a cyanation reaction under the action of a catalyst and a solvent. This reaction has the advantages of mild conditions, low toxicity, high safety, and high conversion rate. The obtained product can be brominated and fluorinated to obtain perfluoroisobutyronitrile. The method has simple equipment, low investment and operation and maintenance costs, simple and safe operation, and a high overall yield of perfluoroisobutyronitrile. In addition, the solvent in this process can be recycled, and the subsequent purification and treatment of perfluoroisobutyronitrile is simple, which is suitable for large-scale production.

[0062] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for synthesizing perfluoroisobutyronitrile, comprising the following steps: S1. Add 35g of p-toluenesulfonylmethyl isocyanide, 13.5g of ethanol, 50g of acetonitrile and 27g of sodium methoxide to a 500mL stirred reactor, stabilize the reactor temperature at -10°C and evacuate to vacuum, then introduce 16.6g of hexafluoroacetone and stabilize the reactor temperature at 0°C to react; after the reaction is completed, discharge the material in the reactor and filter and separate the liquids, collect the lower fluorinated layer, and obtain 3,3,3-trifluoro-2-(trifluoromethyl)propionitrile; S2.

1. Add 17.7g 3,3,3-trifluoro-2-(trifluoromethyl)propionitrile, 35g (0.2mol) liquid bromine and 54g acetonitrile to a 250mL stirred reactor, and set the reactor temperature to 30°C; during the reaction, collect the system liquid for gas chromatography testing, and when the 3,3,3-trifluoro-2-(trifluoromethyl)propionitrile in the reactor is completely consumed, stop the reaction and cool the reactor to 0°C; add sodium bisulfite solution to the reactor, and when the system becomes colorless, separate 2-bromo-3,3,3-trifluoro-2-(trifluoromethyl)propionitrile; S2.

2. In a 250mL stirred reactor, add 25.6g 2-bromo-3,3,3-trifluoro-2-(trifluoromethyl)propionitrile, 16g HF and 25.2g AlF3 respectively, and gradually increase the temperature of the reactor to 80°C; during the reaction, collect the system gas for infrared testing, and when the 2-bromo-3,3,3-trifluoro-2-(trifluoromethyl)propionitrile in the reactor is completely consumed, stop the reaction and cool the reactor to 10°C; release the gas in the reactor and wash with alkaline solution to obtain perfluoroisobutyronitrile.